1. Field of the Invention
This invention relates to a d. c. charged particle accelerator. The invention is applicable to an accelerator for accelerating positive ions in ion implantation apparatus.
2. Background Information
Ion implantation may require the production of ion beams at high energies and high beam current. D. c. accelerators are known to be used in ion implanters for providing the required beam energy.
In a known charged particle accelerator, a number of accelerator electrodes define successive acceleration gaps. The accelerator electrodes are biased at regular voltage intervals to control the voltage gradient along the length of the accelerator. Bias voltages for the accelerator electrodes are derived from a potential divider connected to a high voltage generator providing the full accelerator potential, which may for example be several hundred kilovolts or in excess of one megavolt. A known high voltage generator for this purpose is a Cockcroft Walton voltage multiplying circuit.
There are challenges in designing a d. c. particle accelerator which can operate at relatively high energies and also maintain good stability at high beam currents.